1. Field of the Invention
The invention relates to hard ground cleaning devices, more particularly, to an automatic ground cleaning vehicle.
2. Description of the Related Art
An automatic ground cleaning vehicle generally comprises a cleaning member and a stain suction member. The stain suction member comprises a suction pump, an air suction pipe connected to the suction pump, a water wiper, a stain suction pipe connected to the water wiper, a floating ball, a waste water tank, and an airtight cover serving to cover the top of the waste water tank. When the suction pump is being rotated, a suction pressure is formed inside of the waste water tank, then the stains, which mainly include dust contained waste water and foam, on the ground is sucked into the waste water tank through the stain suction pipe. However, when in use, the suction pump is often burnt out due to the water or foam sucked therein, this is especially serious when high sudsing detergent is used. The original way to eliminate this risk is to lower the liquid level of the waste water tank, however, by this way, the utilization of the waste water tank capacity is decreased, and thereby the working cycle of the waste water tank is shortened. FIG. 4 illustrates a superstructure of a waste water tank of an existing automatic ground cleaning vehicle, the liquid level of the waste water tank is controlled by means of a block sealing method. Namely, when the liquid level of the waste water tank rises to a certain height, the floating ball is catched up by the suction mouth, the suction pressure inside of the waste water tank is then released, the water wiper loses its capability to suck the waste water so that the liquid level of the waste water tank is controlled. However, especially in a noisy environment, even an experienced operate is difficult to differentiate the voice when the suction pump is blocked compared with the voice when the suction pump is not blocked, to say nothing of a fresh operator.